Uma análise da determinação da condutividade hidráulica do solo pelo método do perfil instantâneo

Abstract

An analysis of soil water hydraulic conductivity determination by means of instantaneous profile method The soil water hydraulic conductivity K is a property that expresses the ability of the soil in conducting water. It is of extreme importance to the agricultural management and, consequently, to the soil and environment preservation. The soil water hydraulic conductivity can be determined by means of laboratory and field methods, one better experimentally controlled and the other with less degree of soil disturbing. Among the field methods, the instantaneous profile one is the most used. It was simplified by Libardi et al (1980) that obtained theoretically a relation between the soil water content and the soil water redistribution time assuming unit soil water total potential gradient. In order to analyse in more detail the method, the objective of this work was to obtain an equation similar of the Libardi et al (1980) model but without assuming unit gradient. The study was developed with data of four soils (17 soil depths) from literature and the validation of the equation was carried out by comparing the K() function obtained from it and the K() function tradicionally obtained. From the results, it could be conclude that the  as a function of t proposed equation showed to be valid and according to it the potential gradient may affect both  and K 0 parameters of the K = K 0 exp [(-0)] equation. However, for studied soils the influence of the gradient on the  parameter was irrelevant in comparison with the influence of the gradient on the K 0 parameter, which leads to the possibility of utilization of a mean gradient to obtain K() function. Besides, it could also be conclude that the procedure to calculate the flux density from the equation of soil water storage as a function of redistribution time is much more simple than the procedure proposed by Hillel et al (1972) for this purpose, in the instantaneous profile method.